Four Senators to Watch in the Trump-Russia Investigation

They are a disparate foursome: the chamber’s leading Republican centrist, a minister who embraces public service as a calling, a seasoned dealmaker and a high-profile presidential contender.

These four Republican senators — Susan Collins of Maine, James Lankford of Oklahoma, Roy Blunt of Missouri and Marco Rubio of Florida — are emerging as a bloc integral to the Senate Intelligence Committee’s investigation into Russian meddling in the 2016 presidential election.

The investigation is widely considered the premier inquiry, the one with the necessary jurisdiction and the best chance of producing a credible outcome. These four senators loom large as a crucial element in getting there.

Despite early skepticism about the Republican-led panel’s commitment to the investigation, the four have made it clear that they are determined to see it through to a conclusion that would satisfy the public and their colleagues in both parties. To get there, they will have to slog through thousands of pages of raw intelligence held by the C.I.A. and devote untold hours to grinding committee work behind closed doors.

“This is not about the president, this is about the presidency,” said Mr. Lankford, who was a longtime Baptist youth minister before he entered politics. “This is about where we are as a nation.”

This is not to say that other members of the panel aren’t engaged. The committee’s seven Democrats are certainly interested in finding out whether Russians colluded with the Trump campaign and helped to elect him.

Senator Richard M. Burr, Republican of North Carolina and the chairman of the panel, has shown an increasing zeal for pursuing the question after an uncertain start. He and Senator Mark Warner of Virginia, the committee’s ranking Democrat, have forged a solid working relationship.

Three other Republicans are also playing a role: John Cornyn of Texas, who as the No. 2 Senate Republican brings a leadership perspective to the investigation; Jim Risch of Idaho; and Tom Cotton of Arkansas.

But it is notable that the other four have quietly coalesced into something of an informal working group within the Intelligence Committee, pushing the investigation forward and consulting not only with each other and Mr. Burr, but also with Mr. Warner.

“We are working very hard and we talk a lot with one another, as well,” said Ms. Collins, who said the investigation would “take as long as required.”

“This is a complex investigation, and as you pull the threads, you find that it is connected to a whole lot of other threads in this tapestry that we are not yet seeing the whole of.”

Here is a look at the four and what is driving them.