Mark Warner was in the governor’s mansion the last time a Republican state delegate in Virginia had to fend off a primary challenger. On Tuesday, five do.

What has inspired most of this year’s GOP insurgents is the same thing that sparked the intraparty upstarts in Warner’s day: taxes.

In 2004, Warner (D) persuaded 17 Republicans to go along with a $1.5-billion-a-year tax hike. Anti-tax activists vowed to seek revenge and in 2005 put up six primary challengers.

This year, 34 House Republicans supported a transportation funding overhaul that imposed a $1.2-billion-a-year tax increase. Anti-tax activists again rose up, mounting four of the primary campaigns. (The fifth, involving an incumbent who opposed the roads plan, turns on other issues.)

“The Republican insiders think raising taxes and growing government is a good idea, and they will find out over time — this time or in the future — that it’s not,” said Michael I. Rothfeld, a longtime Virginia-based political consultant who has not worked on these campaigns but said he has given money to three of the challengers.

Candidate guide to the 2013 Virginia primary election

Even though the presence of any GOP primary challenger is notable, some political observers were surprised that there were not more on the ballot given recent displays of tea party muscle in the state. They note that grass-roots activists steamrolled establishment Republicans at a May 18 convention by nominating Chesapeake minister E.W. Jackson for lieutenant governor.

Earlier, the activists had upended the nomination process, scrapping plans to choose statewide candidates in Tuesday’s primary in favor of the convention. That led Lt. Gov. Bill Bolling, an establishment favorite, to abandon his bid for governor against Attorney General Ken Cuccinelli II ( R), a tea party hero. Bolling supported the transportation plan, while Cuccinelli called it a “massive tax increase.”

“Navigating the Republican Party right now is like walking through a roomful of mirrors,” said Quentin Kidd, professor of political science at Christopher Newport University. “On the one hand, you see this real right-wing energy and passion in the convention. . . . But when you disperse them across 100 House of Delegates districts . . . that level of energy dissipates.”

The circumstances surrounding the two tax increases were different. Republicans who signed on to Warner’s tax hike were defying their party leadership to help a Democratic governor. Those who went along with this year’s transportation deal did so at the behest of Republican Party leadership, which observers say might make the tax vote less objectionable to some GOP voters.

In his last year in office, Gov. Robert F. McDonnell (R) was eager to find a way to pay for roads, highways and rail in a state saddled with some of the nation’s worst traffic and on track to run out of new construction funds by 2017. He proposed an $845-million-a-year plan that relied heavily on redirecting existing state revenue. What emerged from the General Assembly was a $1.4-billion-a-year plan that called for $1.2 billion in new revenue.

The deal drew howls not only from anti-tax activist Grover Norquist but also from some rank-and-file Republicans. Even with McDonnell, Bolling and House Speaker William J. Howell (R-Stafford) pushing hard for it, only half of the GOP caucus signed on.

The four Republican incumbents being challenged for supporting the deal are Howell, who faces Craig Ennis; Del. Beverly J. Sherwood (Frederick), who is opposed by Mark J. Berg; Del. Joe T. May (Loudoun), who is up against Dave LaRock; and Del. Robert D. “Bobby” Orrock Sr. (Caroline), who is challenged by Dustin Curtis.

Del. C. Todd Gilbert (Shenandoah), who opposed the transportation deal, faces a challenge from Mark Prince, a Toms Brook cattle farmer and tea party activist. Prince, a former airline pilot, is running on a platform of reducing state and local government debt.

Also facing challengers Tuesday are two Democratic incumbents. Del. Rosalyn R. Dance (Petersburg), who drew criticism from her party this year because she considered supporting a GOP Senate redistricting plan, is opposed by Evandra D. Thompson. Del. Algie T. Howell Jr. (Norfolk) faces police officer Rick James, who also challenged him in 2011.

Political observers do not expect Ennis, who has raised $643, to topple William Howell, who has more than $336,694. But they do not rule out an upset or two in contests that typically draw few voters.

“Do not underestimate that [anti-tax activist] group, because, certainly in an off year, they can play an incredible role,” said Robert E. Denton Jr., a Virginia Tech professor focused on political communication, referring to the modest number of challengers.

Bolling said the GOP primary battles reflect the party’s internal struggle between pragmatism and ideological purity.

“There is a group within our party right now, if you don’t agree with them 100 percent of the way, 100 percent of the time, you’re persona non grata,” said Bolling, who is backing all of the incumbent Republicans through his political action committee, the Virginia Mainstream Project.

The incumbents might take comfort that in 2005, challengers took down just one sitting delegate, Gary Reese of Fairfax, who on different occasions voted for and against Warner’s tax increase.

They might likewise be cheered by the experience of Del. John A. Cosgrove (R-Chesapeake), who voted for the transportation bill and is running for the Senate seat being vacated by the retiring Sen. Harry B. Blevins (R-Chesapeake). Cosgrove drew two challengers who were highly critical of his vote but easily defeated them in a “firehouse primary” in May.