US president Trump gives thumbs up during campaign rally in Cleveland, Ohio. Photo: reutersDonald Trump faced greater restraints on his presidency and intrusive investigations from Democrats who won control of the US House of Representatives and pledged to hold the Republican accountable after a tumultuous two years in the White House.Trump and his fellow Republicans expanded their control of the US Senate in Tuesday’s midterm elections, following a divisive campaign marked by fierce clashes over race and immigration.But they lost their majority in the House, a setback for the president after a campaign that became a referendum on his combative leadership.The split power in Congress combined with Trump’s expansive view of executive power could herald even deeper political polarization and legislative gridlock in Washington.The Democrats will now head House committees that can investigate the president’s tax returns, possible business conflicts of interest and any links between his 2016 election campaign and Russia.There may be some room, however, for Trump and Democrats to work together on issues with bipartisan support such as a package to improve infrastructure or protections against prescription drug price increases.Trump made an unlikely gesture toward Nancy Pelosi, the leader of the House Democrats who he has frequently ridiculed, saying her party should pick her to be House Speaker in the new Congress that convenes in January.”In all fairness, Nancy Pelosi deserves to be chosen Speaker of the House by the Democrats. If they give her a hard time, perhaps we will add some Republican votes. She has earned this great honor,” Trump wrote on Twitter.Earlier on Wednesday, he was less conciliatory, describing the elections results as a “very Big Win” and taking a swipe at the media. Trump was due to hold a news conference at the White House at 11:30 a.m. (1630 GMT).The Democrats fell short of a tidal wave of voter support that would have won them control of both chambers of Congress. But in the 435-member House, the party was headed for a gain of around 30 seats, beyond the 23 they needed to claim their first majority in eight years.A Senate majority would have allowed Democrats to apply even firmer brakes on Trump’s policy agenda and given them the ability to block any future Supreme Court nominees.The House Democrats could force Trump to scale back his legislative ambitions, possibly dooming his promises to fund a border wall with Mexico, pass a second major tax-cut package, or carry out his hardline policies on trade.“Today is more than about Democrats and Republicans, it’s about restoring the Constitution’s checks and balances to the Trump administration,” Pelosi told supporters at victory party.Losing the House will test Trump’s ability to compromise, something he has shown little interest in over the last two years with Republicans controlling both chambers of Congress.He hit back at the prospect of investigations by House Democrats, saying on Twitter that Republicans in Senate would counter with their own investigations of Democrats.GRIDLOCK?US stocks opened higher on Wednesday after the elections, while the dollar dropped on the reduced chances of further US fiscal stimulus.Financial markets often favor Washington gridlock because it preserves the status quo and reduces uncertainty.A Democrat-controlled House will hamper Trump’s pro-business agenda and could lead to uncertainty about his administration, but corporate tax cuts and deregulation measures that have played a large hand in the US stock market’s rally since the 2016 election are likely to remain untouched.”With the Democrats taking over the House we will now have to see what gridlock in Congress means for policy. As for the market impact, a split Congress has historically been bullish for equities and we expect to see the same pattern again,” said Torsten Slok, Chief International Economist of Deutsche Bank.Democrats will use their new majority to reverse what they see as a hands-off approach by Republicans toward Trump’s foreign policy, and push for tougher dealings with Russia, Saudi Arabia and North Korea.Foreign policy has been an area that Trump has approached in a very personal way, sometimes antagonizing allies such as Canada while making what critics see as unduly warm overtures to traditional rivals or foes.Tom Perez, chairman of the Democratic National Committee, said Democrats could work with Republicans to produce a long-awaited bill to upgrade the nation’s roads, bridges and airports.”Of course, we want to work in a bipartisan fashion. I think we can get an infrastructure bill,” he said.Trump had hardened his rhetoric in recent weeks on issues that appealed to his conservative core supporters. He threw himself into the campaign, issuing warnings about a caravan of Latin American migrants headed through Mexico to the US border and condemnations of liberal American “mobs” he says oppose him.DEMOCRATIC PROBESEvery seat in the House was up for grabs on Tuesday and opinion polls had pointed to the Democratic gains. The party with the presidency often loses House seats in midterm elections.The Republicans had an advantage in Senate races because elections were held for only 35 seats in the 100-member chamber and many of them were in states that often lean Republican.Republicans built on their slim Senate majority by several seats and ousted four incumbent Democrats: Bill Nelson in Florida, Joe Donnelly in Indiana, Heidi Heitkamp in North Dakota and Claire McCaskill in Missouri.Those gains are sure to bolster Republicans’ efforts to get conservative federal judges through confirmation proceedings. In the 36 gubernatorial contests, Democrats won in several states that supported Trump in 2016 but lost high-profile races in Florida and Ohio.Democrats could infuriate Trump by launching another congressional investigation into allegations of Russian interference on his behalf in the 2016 election. A federal probe by US Special Counsel Robert Mueller into Russia’s role in that election is ongoing.Moscow denies meddling and Trump, calling the Mueller probe a witchhunt, denies any collusion.A House majority would be enough to impeach Trump if evidence surfaced of collusion by his campaign, or of obstruction by the president of the federal investigation. But Congress could not remove him from office without a conviction by a two-thirds majority in the Republican-controlled Senate, an unlikely scenario.Most Democratic candidates in tight races stayed away from harsh criticism of Trump during the midterm campaign’s final stretch, focusing instead on bread-and-butter issues like maintaining insurance protections for people with pre-existing medical conditions, and safeguarding the Social Security retirement and Medicare healthcare programs for senior citizens.WOMEN, YOUNG, HISPANIC VOTERS FUEL GAINSThe Democratic gains were fueled by women, young and Hispanic voters, a Reuters/Ipsos Election Day poll found. Fifty-five percent of women said they backed a Democrat for the House this year, compared to 49 percent in the 2014 midterm congressional election.A record number of women ran for office this election, many of them Democrats. There were 237 women on ballots for House seats and at least 95 had won their races as of early Wednesday morning, shattering the previous record of 84 women in the House, according to the Center for American Women and Politics at Rutgers University.The party picked up seats across the map but some of the campaign’s biggest Democratic stars lost.Liberal Beto O’Rourke’s underdog Senate campaign fell short in conservative Texas against Republican Ted Cruz. Andrew Gillum lost to Republican Ron DeSantis in his quest to become Florida’s first black governor.In Georgia, Democrat Stacey Abrams was seeking to become the first black woman to be elected governor of a US state. Her opponent, Brian Kemp, was ahead in a very close race early on Wednesday and Abrams said she would not concede until all the votes were counted.