Sen. Marco Rubio will dine with President Trump tonight, part of President Trump's efforts to establish a rapport with members of Congress.

  • Sen. Rubio dining at the White House with President Trump
  • Rubio called it a mostly social dinner
  • Rubio is the latest to call for adding the Flynn case in an investigation of Russia's election involvement
  • D.C. DIGEST: Latest News | Find your Congressman | Washington D.C. Calendar

Rubio, R-Florida, and his wife will join the president and the first lady for dinner around 6:30 p.m.

Rubio did not share what he planned to discuss with the president when speaking to reporters, calling it "mostly a social" dinner.

Rubio, a former presidential campaign rival who called Trump a con artist during the presidential primaries, has largely fallen in line with the Republican Party since, backing all of the president's Cabinet nominees. 

He did show some concern about Secretary of State Rex Tillerson, but he eventually voted for him.

But Rubio is also trying to position himself as a lawmaker who can break away from the party line on matters of principle.

On Wednesday, Rubio became the latest Republican lawmaker to call for an investigation into former National Security Adviser Michael Flynn's discussions with the Russian ambassador.

He also tweeted Wednesday that Andrew Puzder's withdrawal as the Labor Secretary nominee was the "right and honorable choice."

Lately Rubio has made human rights violations a cornerstone of his legislative work. His criticism of Rex Tillerson stemmed from Tillerson avoiding condemnation of several countries over civil rights abuses.

Last week, as Democrats held late night speeches against several controversial Cabinet nominees, Rubio used the time to shine a light on human rights abuses in China, Russia and Venezuela, making a point to say that while Americans enjoy the ability to dissent, those dissenters in other countries would be imprisoned or killed.

In the last few weeks Rubio has taken a harder line on Russia than Trump has. In speeches he's doubted any efforts to get Russia to fight ISIS in exchange for lifting U.S. sanctions against the country.

"I think this whole notion of a grand bargain, where they are going to help us kill terrorists and fight ISIS in exchange for lifting sanctions, is a fantasy," Rubio said last week.

Calls to Sen. Rubio's office for a statement were not returned.

Information from CNN was used in this report.