Sen. Jeff Flake, girding for a challenging re-election bid in 2018, raised $1.1 million in badly needed cash in the third quarter of this year, to close the period with $3.4 million his campaign account.

The Arizona Republican, at odds with President Trump, must first contend with the possibility of a competitive Republican primary. Trump has subtly encouraged others to run for the GOP Senate nomination in Arizona, and Flake's primary opponent at this point, Kelli Ward, has received some initial support from the Mercer family, funders of other populist insurgents.

If Flake wins re-nomination, Rep. Kyrsten Sinema, D-Ariz., will likely be waiting for him in the general election. She could be formidable, if for no other reason than Democrats are likely to invest in her race as one of only two where Republicans are vulnerable in the midterm. Flake is going to need resources to defend himself.

"This is yet another impressive fundraising quarter from Jeff Flake and the campaign remains well-positioned to win," Flake spokesman Will Allison said in a statement emailed to the Washington Examiner.

Flake has raised $4 million so far this year, and help is on the way in the weeks ahead. Sen. Marco Rubio, R-Fla., is headed to Arizona this month to headline a fundraiser for his colleague. Condoleezza Rice, the former secretary of state under President George W. Bush, is also scheduled to raise month for the senator.

Democrats are defending nine incumbents in states Trump won in 2016, making Flake and Sen. Dean Heller, R-Nev., targets of opportunity.