WASHINGTON - The midterm elections to be held on Tuesday are the first major electoral battle since US President Donald Trump clinched the White House. Now, after two years, Democrats are eager to get back in the ring and slug it out with the GOP.

But no one has a crystal ball to tell who will win, especially after pundits, polls and political soothsayers have been wrong before.

The wild card in this year's midterms is the House of Representatives, while Republicans are expected to keep control of the Senate.

Democrats need to take away at least 23 Republican seats to have control of the House. On Saturday, the often-cited Real Clear Politics "Battle for the House 2018" poll had Democrats ahead by 203 to 196. The race has been tighter in recent weeks, with Democrats making gains even in areas that tend to lean conservative, the nonpartisan Cook Political Report found.

There are currently 17 Republican-held districts that are seeing a slight or strong lean toward Democrats, mainly in upper-middle-class suburbs, including in the states of New Jersey and Pennsylvania.

However, Republicans have gained ground in some rural districts, such as outside the cities of St. Louis and Cincinnati, where conservatives have rallied to support Trump, according to the Cook report.

"Trump definitely has galvanized the Democratic base and it is likely to turn out in big numbers on Tuesday," Brookings Institution Senior Fellow Darrell West said.

Republican Strategist and TV news personality Ford O'Connell, however, said that while historical precedent is in Democrats' favor, "the only question here is whether the Republicans in the House can minimize their losses and hold onto the House by a sliver".

Christopher Galdieri, an assistant professor at Saint Anselm College, said Democrats "have been fired up about 2018 since shortly after the 2016 election".

"We've seen evidence of that in the number of strong candidates running, including in districts that have not had competitive races in years, Democratic fundraising, and shifts toward Democrats in special elections for Congress and state offices in 2017 and 2018."

But a win is not necessarily in the bag. "That does not mean winning the House is a lock, by any means," he said.

As the race tightens, Trump has been on the campaign trail to rally Republican voters and appeared in Florida and Montana on Saturday

At both events, Trump talked up the economy and tax cuts, new Supreme Court Justice Brett Kavanaugh, border security and several caravans of Central American migrants who are slowly advancing toward the US-Mexico border.

He mentioned plans for a new military branch called the Space Force, and complained anew about the news media.

Trump also defended his decision to focus almost exclusively on the migrants and immigration in the closing days of the election. He recently announced that he intends to change asylum procedures, end the constitutional guarantee of birthright citizenship and build numerous "tent cities" to hold migrants caught crossing the border illegally.

"You can only say so many times that we created 250,000 jobs last month," Trump said in Montana, in defense of his focus on immigration that some of the president's critics say amounts to fearmongering.

"When we're fixing a problem or fixed a problem there's no reason to go on about it for 45 minutes."