No matter what the polls show, Republicans have reason for optimism in their effort to take Congress from Democratic control in the midterm elections next week. And it is history.

The party out of power almost always picks up seats in Congress in midterm elections. And Republicans need to pick up just five out of 435 in the House to grab the majority and just one out of 35 in the Senate.

For decades, "it has usually been that the party in power expects a wake-up call" in the midterm elections, said Laura Smith, a presidential historian at Oxford University. "Americans have tended to vote in divided government in the midterms as a bit of a slap in the face to the sitting president."

In the past four decades, the only times when a sitting president's party has won seats in the midterms has been in 1998 (Bill Clinton's second term) and 2002 (George W. Bush's first term). Both presidents had high approval ratings then.

According to a recent Gallup poll, President Joe Biden's approval rating is 40 percent, a step down from the 44 percent measured in August but still above his term-low 38 percent from July.

All 435 House seats are up for election. The Cook Political Report rates 31 races as toss-ups — 22 of which are currently held by Democrats and nine by Republicans. A shift of five seats would transfer control of the chamber to Republicans.

The GOP taking the House means Republicans will run every committee, decide what bills come to the House floor and either block or disrupt the Biden administration agenda for the last two years of his term.

Beyond history, frustration over the economy with the highest inflation rate in 40 years, a steady rise in the cost of living, immigration, and advantages in the redistricting process that takes place every 10 years favor Republicans to win the House.

With a record number of migrants and asylum seekers crossing the southern border this year, Republicans have turned opposition to Biden's immigration policies into a political rallying cry, saying his administration is failing to secure the border.

While Democrats argue that inflation is linked to global events, such as the war in Ukraine, and coronavirus pandemic-related supply chain issues, Republicans say government spending, which has accelerated under Biden, is to blame.

For Democrats, midterm issues include access to abortion, healthcare, climate change and concerns about the future of democracy and fair elections in the country.

Democratic candidates argue that a Republican return to power could fundamentally harm the governing system in the country, especially with the GOP having nominated candidates who didn't accept the 2020 election results up and down the ballot across the country.

"It is a really unusual election," said Republican pollster Bill McInturff of Public Opinion Strategies. "Republicans have significant advantages on their set of issues (inflation, economy, crime, border security) and Democrats enjoy significant advantages on issues of concern to their voters (abortion, climate change, guns, healthcare). There is no overlap, no competitive issues. This means each party has an unusual opportunity to try to create their own narrative to their own voters on what this election is about."

A return to Republican power in the House would be a victory for Trump, who has fought Democrat-led efforts by the House Select Committee to hold him accountable for the Jan 6, 2021, storming of the Capitol.

Most Republicans who are expected to return to Washington next year, along with most of those hoping to win a first term, are loyal to Trump and have followed his example in their policies and positions. In the Senate, the split now is even, 50-50, with Democratic Vice-President Kamala Harris breaking ties.

If Democrats increase their majority in the Senate, they could have enough votes to break through the filibuster on key issues for their party, from voting rights to gun control. They might also move to codify abortion rights and same-sex marriage into federal law.

"If you give me two more senators in the United States Senate," Biden said recently, "I promise you, I promise you, we're going to codify Roe and once again make Roe the law of the land."

A Republican-led Senate could pass bills sent over by a GOP House, and the Republicans would regain control of committees and the power to conduct investigations and oversight of the administration, which they have vowed to do.

Some House Republicans have talked about launching investigations against the Jan 6 committee members themselves, whether the president's son, Hunter, committed tax fraud and lied to pass a background check to buy a gun, the FBI's search of Trump's Florida residence Mar-a-Lago and Biden's border policy.

A Republican Senate also could block or delay passage of the president's nominees. It also could stymie Biden's plan boosting appropriations to enlarge the Internal Revenue Service, which he got with a provision in the climate and healthcare bill passed by Congress.

Republicans complain that adding more IRS agents would lead to harassment of small businesses. Democrats say more agents would crack down on wealthy tax evaders, including large public corporations, which could pressure their stocks.

Although a Republican Congress and a Democratic White House could lead to legislative gridlock, there are some areas where lawmakers might reach bipartisan agreements. An analysis from Morgan Stanley Wealth Management listed greater defense spending, cybersecurity, supply-chain strengthening and tech regulation.

Democratic priorities such as access to abortion, addressing climate change and stricter gun control would be sidelined. And most, if not all, of Biden's agenda would be effectively dead for the final two years of his term.

If Democrats keep the House and the Senate, they will act to pass some of Biden's agenda items, including his new package of social and economic programs that stalled amid internal Democratic disagreements.

Agencies contributed to this story.