Ron Paul won't campaign in any more primaries, his campaign announced Monday afternoon.

A letter sent from Paul to supporters promised to continue the battle for delegates at state party conventions in order to try to influence the party's platform, but said the campaign will no longer try to win delegates in new states — an uphill battle now that Mitt Romney is the presumed nominee and most states have gone to a winner-take-all system of delegate apportionment.


"We will no longer spend resources campaigning in primaries in states that have not yet voted," Paul said in the letter. "Doing so with any hope of success would take many tens of millions of dollars we simply do not have."

Paul had already scaled back his efforts in states as compared to the heavy spending he'd done in early elections like Iowa, New Hampshire and Nevada, and the timing of his decision means he won't campaign in his home state of Texas, which will vote on May 29.

The letter promises to lay out the campaign's delegate strategy for the Republican National Convention and asks supporters to "stay tuned" for further strategy updates — two words that may make Romney's campaign nervous that Paul's supporters will cause problems at the early September convention.

Paul's supporters have continued to organize and agitate for delegates in caucus states that have yet to name their delegates to the convention, including Iowa, Nevada and Minnesota, creating a degree of uncertainty to the convention process. But at its heart the letter means a suspension of Paul's libertarian-tinged presidential campaign.

This post was updated at 2:40 p.m.