Six weeks ago, back when Romney seemed ascendant, Jon Walker commented that Mitt Romney would do well to be very, very nice to Ron Paul, as Paul holds Romney’s fate in his hands:

With Mitt Romney now on a glide path to the Republican Party’s nomination, there is one thing that could completely doom his chances of becoming President and that is Ron Paul. Paul’s dedicated base might not be large enough for him to win the nomination, but it is large enough to destroy Romney’s hopes in the general.

A week later, the Washington Post reported on the friendship — and de facto alliance — between Mitt Romney and Ron Paul:

The remaining candidates in the winnowed Republican presidential field are attacking one another with abandon, each day bringing fresh headlines of accusations and outrage.

But Mitt Romney and Ron Paul haven’t laid a hand on each other.

They never do.

[...]

Romney’s aides are “quietly in touch with Ron Paul,” according to a Republican adviser who is in contact with the Romney campaign and spoke on the condition of anonymity to discuss its internal thinking. The two campaigns have coordinated on minor things, the adviser said — even small details, such as staggering the timing of each candidate’s appearance on television the night of the New Hampshire primary for maximum effect.

One advantage for Romney is that Paul’s presence in the race helps keep the GOP electorate fractured. But there is also a growing recognition that the congressman plans to stay in the contest over the long term — and that accommodating him and his supporters could help unify Republican voters in the general election against President Obama.

“Ron Paul wants a presence at the convention,” the adviser said — and Romney, if he is the nominee, would grant it.

Of course Romney would grant it. As Jon Walker said six weeks ago:

If I were Romney I might even consider using the excuse of “reaching out to Paul’s base for the sake of party unity” as a convenient way to justify tacking to the left after basically securing the nomination.

And now, this week, Rick Santorum’s finally picked up on all of this:

Asked at a Tea Party rally here why former Massachusetts Gov. Mitt Romney and Rep. Ron Paul of Texas seemed to be ganging up on Santorum during Wednesday’s debate in Arizona, the former senator from Pennsylvania quipped, “Yeah, look, I didn’t know we picked president and vice president before the election.

“The coordination that I felt at that debate was pretty clear,” he said. “I felt like messages were being slipped behind my chair. It’s pretty remarkable that in 20 debates, Ron Paul never attacked Mitt Romney.”

Frankly, I’ve been astonished that Santorum didn’t start publicly addressing this before this week just passed.

More on the Romney-Paul arrangement — or “bromance” — in the video above.