Groups supporting Senators Rand Paul and Marco Rubio lead the pack of potential Republican presidential candidates in spending money and investing in possible campaigns this year, more than 20 months before the first votes are cast in 2016.
No politician has yet declared his or her candidacy, but first-quarter fundraising numbers submitted to the Federal Election Commission and released this week show backers of Rubio and Paul spent several hundred thousand dollars to help both senators in the first three months of 2014.
Kentucky Senator Paul's RANDPAC group spent over $580,000 in the first quarter, much of it on fundraising, consulting, and travel expenses as the first-term lawmaker crisscrossed the country spreading his libertarian message and courting groups that do not traditionally support Republicans.
Paul has built a national infrastructure largely on the back of his father Ron Paul's network from previous presidential campaigns.
Rubio, a Florida senator who has fallen out of favor with many in the party's right wing over his support of immigration reform, has been one of the most active contenders since 2013.
The freshman's Reclaim America PAC raised over $530,000 in the first three months of 2014, and spent over $375,000. Much of that money went to consultants and data analytics teams that could help Rubio if he chose to run for president.
Other possible candidates have been meeting with donors and operatives to set up potential campaigns, but have not been as publicly active as Rubio and Paul. Former Florida Governor Jeb Bush has no similar political committees, for example, while groups associated with Texas Senator Ted Cruz have not raised or spent as much.
Embattled New Jersey Governor Chris Christie demonstrated his own fundraising acumen by leading his Republican Governors Association to a $23.5 million first quarter but he has no federal groups raising money for a possible presidential run.
On the Democratic side, a network of independent organizations has been laying the groundwork for a campaign by former U.S. Secretary of State Hillary Clinton. The first quarter saw increased activity by Priorities USA Action, the primary fundraiser for President Barack Obama in 2012, which now stands behind Clinton.
The group, which is led by Obama's 2012 campaign manager Jim Messina and is expected to be the Clinton campaign's main money vehicle, spent over $535,000 in the first quarter despite not actively fundraising.
It had earlier come under fire for not doing enough to support Democrats in 2014 elections, and it sent $250,000 to the primary PAC supporting congressional Democrats - House Majority PAC - in February.
Last week Ready For Hillary, a super-PAC urging the former first lady and senator to run by building up grass-roots support, announced it had raised more than $1.7 million in the first quarter. That brought its fundraising haul to over $5.75 million since launching in 2013 - despite a self-imposed cap of $25,000 per donation.
Clinton holds a considerable lead over other potential Democratic presidential contenders in preliminary polling.