ROLLINSFORD, New Hampshire — Officially, Sen. Jeff Merkley remains undecided on the prospect of a White House run. But his fourth visit this year to the state that holds the first presidential primary has the look and feel of a campaign swing.

As for 2020, Merkley would only say that he and his wife, Mary Sorteberg, would wait until after the November midterm elections to make a decision.

"We're going to wrestle with that right after the election, and we'll figure it out then and decide on what we're going to do," he said.

Merkley is one of the most progressive members of the Senate and was the only Democrat in the chamber to endorse Sen. Bernie Sander in the 2016 primary over the party's eventual nominee, Hillary Clinton. Sanders was in New Hampshire on Labor Day amid reports the Vermont independent is mulling a second straight White House bid.

Merkley said his decision won't be influenced by the possible candidacies of Sanders or Sen. Elizabeth Warren of Massachusetts.

"I've always fought battles I believe in, and right now I believe that we have to do everything we can to take our nation back," he said. "The decision to be in the campaign will be based on whether it's a fight that Mary and I decide that is the right moment and that I can really contribute to."

In a move that could position him for a presidential run in this crucial primary state, Merkley said that he's hiring some political staffers in New Hampshire through one of his PACs in the coming days to help local candidates running now.

"I'm not staffing up here, but what I am doing is helping to hire folks to help out with some of the New Hampshire campaigns. So, hopefully, in addition to providing some assistance with resources, I'll be able to provide some assistance with some people on the ground as organizers," he explained.

While Merkley's four-day trip sparked more 2020 speculation, it was officially about helping Granite State Democrats on the November ballot.

The senator met Friday afternoon with the University of New Hampshire Democrats. In the evening, he headlined the Strafford County Democrats' annual fall fundraising celebration, an event that Sanders keynoted last year.

In his speech, Merkley pointed to the record Democratic turnout days earlier during the New Hampshire primary. "I sense a difference between my last trip here and now," he said. "After this Tuesday primary and the huge turnout of Democrats, it is going to be a blue wave if we push right through November."

He also highlighted his push for a single-payer Medicare-for-all; single payer health care; debt-free higher education and refinancing college loans at lower rates; ending partisan gerrymandering; his push to battle the opioid epidemic; and his "Mission 100" goal of moving toward 100 percent renewable energy.

Sen. Jeff Merkley, speaking Friday in New Hampshire, says he won't decide on a White House run until after the midterms.

On the increasing divisive battle over Supreme Court nominee Brett Kavanaugh, Merkley called the process "a rigged system" and vowed to push back against President Donald Trump's pick "until the last moment."

And he discussed his trips to the U.S. border with Mexico, which inspired other Democrats to follow in his footsteps and helped spark national protests against Trump's "zero tolerance" immigration policy that separated children from their parents.

Merkley vowed to fight a Senate bill that currently has 35 co-sponsors that would establish internment camps for immigrant families awaiting a hearing. "It is not going to pass," he said. "It is not going to get to the Oval Office."

The senator's trip to New Hampshire comes a few days after he released documents indicating the transfer of nearly $10 million from the Federal Emergency Management Agency to U.S. Immigration and Customs Enforcement, the agency at the forefront of the border controversy.

Merkley's disclosure came during an interview on "The Rachel Maddow Show," one of three appearances he made this week on MSNBC.

"It's $10 million that the administration chose in June to take out of FEMA and send to build prison camps," he told The Oregonian/OregonLive on Friday.

"Why in the first month of hurricane season, after what we went through last year, would you take money out of FEMA?" he said.

Merkely noted that "the Trump team's reaction was to attack me personally, which is generally their reaction to any policy issue ... attack the messenger. But all I was doing was taking numbers from their publication that they apparently didn't want the public to see."

Also on Merkley's itinerary this weekend is a stop in Conway to open a county Democratic Party office, a house party in Concord and a fundraiser in Lee for an executive councilor's re-election, and plenty of meetings with Democratic officials, candidates and top activists. The Senate Foreign Relations Committee member closes out his trip on Monday morning with an address to the World Affairs Council of New Hampshire.

—Paul Steinhauser, for The Oregonian/OregonLive