It signaled that if Cochran decided to run, he would not be assured victory and would have to spend most of the Republican primary working to assure voters that there was no question of his conservative credentials.
Cochran has raised less than $1 million toward his reelection. But what's worse for him is that polling showed he is vulnerable to a primary challenge.
None of that was enough for Cochran to call it quits. Even before he announced his decision to run, his allies predicted that McDaniel, not Cochran, might be the one with a tough road ahead.
"I think he will get his head handed to him, and that will be what he deserves," Mississippi Republican lobbyist Henry Barbour, a Republican National Committee member, told Roll Call of McDaniel's primary challenge. "[But] it's a free country."
There's something to this. As a senate appropriator, Cochran has helped bring money to Mississippi and there's a chance he could retake the chairmanship of the committee, an attractive prospect to Republican voters in a poor state like Mississippi.
McDaniel also isn't without his weaknesses. News broke earlier in the year that McDaniel had attended neo-Confederate and pro-secessionist events throughout the state. Establishment Republicans in Mississippi also have suggested that McDaniel's background as a trial lawyer could prove to be a liability.
"Senator Cochran's opponent's record as state senator and his trial lawyer practice are something that the voters of Mississippi will want to take a closer look at, because it's very different than the commercials that are being funded by out-of-state special interest money," Barbour told The New York Times.
A primary fight between Cochran and McDaniel will also serve as yet another battlefield for the ongoing feud between the Senate Conservatives Fund (which has endorsed McDaniel) and the National Republican Senatorial Committee.
"We support incumbent Republican Senators," National Republican Senatorial Committee Communications Director Brad Dayspring told TPM on Friday in response to being asked whether the committee would jump into the primary on Cochran's behalf.
Cochran himself expressed calm about this next race.
"I'm comfortable with my decision," Cochran said Friday, according to USA Today. "I'm looking forward to it. People have been very generous and expressed appreciation. Some have even started sending contributions and helping in that way."
Even McDaniel himself seemed to acknowledge on Friday that running against Cochran would not be a cakewalk.
"Sen. Cochran has had a long and distinguished career representing the people of Mississippi," McDaniel said in response to Cochran's decision. "I look forward to a positive campaign based on the future of our state, our country and the Republican Party. As a strong conservative, I will fight to bring those values to Washington."