One of the Tea Party's most critical battles is heating up in Texas, where two conservative Republicans will slug it out for their party's Senate nomination later this month.

State and national Tea Party groups are backing former Texas Solicitor General Ted Cruz, who they hope will join a small but growing group of U.S. senators aligned with the conservative movement and pushing an agenda of less government spending, lower taxes and fewer regulations.

Cruz faces David Dewhurst, the state's lieutenant governor, in a July 31 runoff election after finishing at the top of the May 29 primary. Dewhurst beat Cruz by 10 percentage points but fell short of the 50 percent needed to avoid a runoff.

The Texas race has captivated the Republican Right. The popular blog RedState calls it "the most important battle for conservatives this year" and is pushing for a Cruz victory.

In the face of Dewhurst's apparent lead, state and national Tea Party groups are pouring money and manpower into Cruz's campaign.

They want Cruz to join the growing ranks of Tea Party senators, including Jim DeMint of South Carolina, Marco Rubio of Florida, Mike Lee of Utah, Rand Paul of Kentucky, Pat Toomey of Pennsylvania and Ron Johnson of Wisconsin.

And they have good reason to feel hopeful.

The Tea Party has been buoyed by recent Senate primary victories in Indiana and Nebraska, where their candidates came from behind to edge out Republican favorites.

FreedomWorks, a national Tea Party organization, has spent more than $130,000 to defeat Dewhurst, who they say is not as committed as Cruz to fighting the Senate's GOP establishment.

They associate Dewhurst with the state's current GOP senators, Jon Cornyn and Kay Bailey Hutchison, whose support for the Wall Street bailout earned them the Tea Party's derogatory title of "establishment" Republicans.

"David Dewhurst would have voted for that bailout; Ted Cruz would not have," Brendan Steinhauser, FreedomWorks' federal and state campaigns director, said. "We want the Republican Party to be based on certain values and positions, and we want to try to change it from within."

Texas Tea Party activists say Dewhurst is really a moderate, citing his support of the Texas Dream Act, which allows illegal immigrants to pay lower in-state college tuition rates.

But based on campaign pledges and political records, it's hard to tell Cruz and Dewhurst apart. Newspaper articles frequently note that they share the same views on many key issues, including repealing the health care law, lowering federal spending and cutting taxes. Dewhurst said he opposes the federal version of the Dream Act, which provides a path to legal residency for illegal immigrants.

Dewhurst, lieutenant governor since 2003, enjoys the support of Gov. Rick Perry, a Tea Party icon and former presidential candidate. He's backed by many other prominent Texas conservatives and former Arkansas Gov. Mike Huckabee, another important Tea Party figure.

Dewhurst spokesman Matt Hirsch said Cruz's race is being fueled by outsiders like FreedomWorks, while Dewhurst has more support among Texans.

But Hirsch acknowledged that Dewhurst, unlike Cruz, will not commit to aligning himself with the Senate's Tea Party faction, which rejects all compromises that violate Tea Party ideals.

"He is going to be beholden to what is in the best interest of Texans," Hirsch told The Washington Examiner.