The incoming Senate in the 115th session of Congress that will convene in January currently has 52 Republicans and 46 Democrats. Two Independents caucus with the Democrats.

Looking ahead, though, shows a rougher road for Democrats. Some 23 of the 33 Senate seats up in 2018 are held by incumbent Democrats. Two are held by incumbent Independents who caucus with the Democrats (Sen. Bernie Sanders of Vermont and Sen. Angus King of Maine), and only 8 are held by incumbent Republicans.

The magic number for Republicans to reach in order to be able to invoke cloture rules to end a filibuster is 60, thanks to a rules change approved by the full Senate in 1975.

President-elect Trump won the electoral college votes in 10 of the 23 states where incumbent Democrat senators are up for re-election in 2018 (West Virginia, North Dakota, Montana, Missouri, Indiana, Ohio, Florida, Pennsylvania, Wisconsin, and Michigan).

Trump lost the electoral college votes of only one of the eight states where Republican senators are up for re-election in 2018 (Nevada).

Should the 2018 Senate races follow the 2016 Presidential results, Republicans would pick up a net nine seats in the Senate, giving them a total of 61 seats in the upper chamber–one more than the 60 needed to end a filibuster.

Though each race will be determined by unique local conditions as well as the national political trends, Republicans are optimistic that they have a reasonable chance of picking up at least eight net seats that would bring them to the magic number of 60.

The current Republican majority in the Senate could increase to 53 within a few months if President-elect Trump chooses to offer Sen. Heidi Heitkamp (D-ND) a job in his administration as Secretary of Agriculture and she accepts that offer. Several recent media reports call Heitkamp a leading candidate for the job.

Heitkamp narrowly won election to her first term in 2012, when she defeated Republican Rick Berg, 50 percent to 49 percent. Her prospects of winning re-election in 2018 are uncertain at best. North Dakota is one of the 10 states with Democratic senators up for re-election in 2018 where Trump won the state’s electoral college votes. The New York City real estate billionaire easily won North Dakota by a 36 percent margin in the 2016 Presidential general election.

Heitkamp narrowly won election to her first term in 2012, when she defeated Republican Rick Berg, 50 percent to 49 percent.

“If Heitkamp, North Dakota’s sole Democrat in Congress, does become Agriculture secretary, a special election would be held to fill her seat, creating a chance for Republicans to strengthen their Senate majority,” the Grand Forks (North Dakota) Herald reports.

In West Virginia, where Trump defeated Clinton by 42 percent, largely due to her support for President Obama’s efforts to destroy the state’s coal industry, Sen. Joe Manchin (D-WV) was for a time a possible candidate to serve as Secretary of Energy in the Trump administration. That job went to former Texas Governor Rick Perry, and Manchin was offered a leadership role by Senate Democrats, which he accepted.

Despite Trump’s huge victory over Clinton in the Mountaineer State, Manchin remains a favorite to win re-election in 2018 due to his long history as a political figure in the state and his unique ability to convince voters there he is a conservative Democrat with truly populist instincts. Though a party switch by Manchin between now and the election can not entirely be ruled out, if he remains a Democrat he will likely remain a heavy favorite to win re-election unless Republicans can attract a strong well financed challenger.

On Thursday, Manchin told Fox News Channel’s Brian Kilmeade that he would “absolutely” remain a Democrat.

Most troublesome for the Democrats are the huge margins by which Trump won in three other states where Democrat Senate seats are at risk in 2018: Montana (20 percent), Missouri (19 percent), and Indiana (19 percent).

In Montana, Sen. John Tester (D-MT) barely won the 2012 contest over Republican Denny Rehberg, 48 percent to 45 percent.

In Missouri, the resilient and personally wealthy Sen. Claire McKaskill (D-MO) easily defeated former Rep. Todd Akin in 2012, 55 percent to 39 percent, after a number of gaffes by her challenger.

In Indiana, Sen. Joe Donnelly (D-IN) won a 50 percent to 44 percent victory over Richard Mourdock in 2012, the Tea Party favorite who upset incumbent Sen. Rich Lugar (R-IN) in the Republican primary.

Trump also won five key swing states where incumbent Democrat Senators are up for re-election in 2018: Ohio (which he won by 7.6 percent), Florida (1.3 percent), Pennsylvania (1.2 percent), Wisconsin (1 percent), and Michigan (0.3 percent).

Republican challengers will have a reasonable chance of winning in all five of these states.

In Ohio, Sen. Sherrod Brown (D-Ohio) defeated Republican Josh Mandel by a 51 percent to 45 percent margin in 2012. But Brown’s strident far-left voting record and rhetoric appears to be out of step with the more conservative trends of the Buckeye State, so he is probably very vulnerable in 2018.

In Florida, Sen. Bill Nelson (D-FL) easily defeated former Rep. Connie Mack IV 55 percent to 42 percent in 2012. Nelson is a long time political figure in Florida. Though Mack ran a very flawed campaign, unseating Nelson will be a significant–and very expensive–challenge for Republicans in 2018.

In Pennsylvania, Sen. Bob Casey, Jr. (D-PA) easily defeated Republican Tom Smith 53 percent to 44 percent in 2012.

In Wisconsin, first term Senator Tammy Baldwin (D-WI) defeated former Governor Tommy Thompson 51 percent to 45 percent in 2012.

In Michigan, Sen. Debbie Stabenow (D-MI) had an easier victory in 2012. She stomped former Rep. Pete Hoekstra at the polls by a 58 percent to 38 percent margin. But Michigan’s political environment in 2016 and beyond looks very different after Trump’s stunning victory there in November.

Trump won the electoral college votes in seven of the eight states where incumbent Republican senators are up for re-election in 2018 (Tennessee, Nebraska, Mississippi, Utah, Nebraska, Wyoming, and Arizona).

Only in Nevada, where Sen. Dean Heller (R-NV) is up for re-election, did Trump lose, and there the margin was only 4 percent.

At least seven incumbent Democrats up for re-election in 2018 are in relatively safe seats.

In Hawaii, where Clinton won the state’s 2016 electoral college votes with a 32 percent margin, Sen. Mazie Hirono (D-HI) is likely to win re-election, should she choose to run.

In California, where Clinton stomped Trump with a 28 percent margin, Sen. Dianne Feinstein is a heavy favorite to win re-election, but at age 83 she is yet to announce whether she will run again for a six year term that will end in January 2025, when she will be 91. Even should she retire, Democrats are almost certain to retain the seat.

Similarly, Sen. Elizabeth Warren (D-MA) appears safe in the Bay State, where Clinton won by 27 percent, as is Sen. Ben Cardin (D-MD) in Maryland, where Clinton won by 25 percent, and Sen. Kirsten Gillibrand (D-NY) in the Empire State, where Clinton won by 21 percent.

Clinton won by less than 20 percent in eight states Democrat Senate seats are at risk in 2018: Washington, Rhode Island, Connecticut, New Jersey, Delaware, New Mexico, Virginia, and Minnesota.

Though two years is an eternity in politics, even the University of Virginia’s Larry Sabato, who incorrectly predicted a Hillary Clinton electoral college blowout ten days before the 2016 election, is warning that Democrats are “very exposed” in the 2018 Senate elections.

Not all Beltway pundits agree.

The Cook Report, which on November 7 predicted that Hillary Clinton would win the Presidency with at least 278 electoral college votes, giving Donald Trump 214 votes and calling 46 votes as tossups, published its early predictions for the 2018 Senate elections on November 10, and claimed that none of the 33 Senate seats were likely to change parties.

The Cook Report rates five Senate seats up in 2018 currently held by Democrats as “Lean Democrat,” that is, they are “competitive races” but the incumbent Democrat “has an advantage”: Nelson in Florida, Donnelly in Indiana, King (the Independent) in Maine, McCaskill in Missouri, and Brown in Ohio.

Surprisingly, the Cook Report considers eight seats up in 2018 currently held by Democrats as “Likely Democrat,” that is, they “are not considered competitive at this point but have the potential to become engaged”: Menendez in New Jersey (under indictment for public corruption, has not yet said whether he will run for re-election), Stabenow in Michigan, Casey in Pennsylvania, Tester in Montana, Heitkamp in North Dakota, Manchin in West Virginia, Baldwin in Wisconsin, and Kaine in Virginia.