President Trump will host six senators for a bipartisan dinner at the White House Tuesday, three of whom are among the most vulnerable Democrats up for reelection in 2018.

Those members are Sen. Joe Donelly, Ind., Heidi Heitkamp, N.D., and Joe Manchin, W.Va. Each hail from red states where the Trump's margin of victory ranges from 19 to 42 percentage points.

The dinner will also include three Republican senators: Senate Finance Committee Chairman Orrin Hatch, Utah, who is considering retirement at the end of his current term; Pat Toomey, Pa; and John Thune, S.D., according to a White House official.

The occasion comes less than a week after Trump hosted congressional bipartisan leaders at the White House, during which he struck a deal with the top House Democrat Nancy Pelosi, Calif., and Senate Minority Leader Chuck Schumer, N.Y., to combine a three-month extension on the debt ceiling with $15 billion in disaster relief for those impacted by Hurricane Harvey.

By moving forward with Pelosi and Schumer's proposal, Trump discarded a GOP-backed plan which would have extend the debt ceiling for six months or 18 months. Several congressional Republicans later said they were disturbed by the president's decision to side with Democrats over his own party.

Tuesday's working dinner is expected to focus on tax reform, something Trump and Republican lawmakers have promised to make progress on before the end of the year.

Because of the risks they face heading into midterm elections, Donnelly, Heitkamp and Manchin may be more likely to lend their support to a GOP tax package that includes widespread cuts and reforms to the current structure.

Heitkamp appeared at a tax reform event last week where Trump pushed for a business tax rate around 15 percent and a full repeal of the estate tax. The North Dakota Democrat traveled with the president on Air Force One to the event.