Sen. Ted Cruz, R-Texas, has not been engaged in his role as vice chairman of the National Republican Senatorial Committee, according to multiple sources familiar with GOP politics, and a growing number of Republicans are frustrated that the freshman senator has aligned himself with a group actively attacking their incumbent colleagues.

Cruz’s profile has elevated in recent weeks with his aggressive campaign against the president’s health care law, including an expensive and profitable anti-Obamacare fundraising spot for the Senate Conservatives Fund that has aired nationwide. But his position with the NRSC as vice chairman for grass-roots outreach — which these sources said never was clearly defined in the first place — seems in tension with his work with the SCF. And his lack of involvement at the NRSC raises the question of why he would want to be affiliated with the group at all.

“The vice chairman of the NRSC is actively raising money for an organization going after Republican senators,” one GOP aide bluntly observed.

Cruz spokeswoman Catherine Frazier said, “The senator is committed to working with Republicans to win the majority in 2014.”

“He has said before that he is unlikely to get involved in any primary races unless it’s an open seat and a candidate has significant grass-roots support,” she added.

Said NRSC spokesman Brad Dayspring: “Outside organizations and groups in both parties have their own goals, agenda and tactics and any senator who feels compelled to support them [is] certainly free to — pretty status quo for politics.”

Roll Call reported in January that, “Cruz’s role as vice chairman of grass-roots outreach appears thus far to be rich in symbolism but light on substance.” Since then, the substance has gotten even lighter and the symbolism murkier.

It’s helpful for the NRSC to look like it cares about grass-roots voters. It’s less helpful for the NRSC to have the person who is the face of that effort on television for the Senate Conservatives Fund, which is currently “polling” its membership on whether to support Senate Minority Leader Mitch McConnell of Kentucky in a primary, citing his “liberal record” in Washington. Given the “symbolic” nature of the position, however, sources said it would look worse for the NRSC to try to remove Cruz than it would be for the group to keep him around in title only. And neither party has indicated an intent to part ways formally.

Fellow conservative Rand Paul of Kentucky, for example, has backed off of his involvement with the SCF because he publicly backs McConnell and the group is unlikely to do so. A GOP source indicated that the SCF has spent about $500,000 on TV and radio in seven states with incumbent senators, including Kentucky.

Dayspring brushed off Cruz’s work with the SCF. “Our focus is simple: Winning the majority and this week is just another reminder of why that is so important. … The liberal media may want to gang up on Ted Cruz this week because of his opposition to ObamaCare and willingness to fight for what he believes in, but we simply aren’t going to be a part of that. There are two facts to remember this week: First, the majority of the country opposes ObamaCare. Second, when Republicans fight for and with each other, we win,” the spokesman said in an email.

In August, NRSC Chairman Jerry Moran of Kansas said one of the top missions of the group is to defend incumbents, whom he called his “constituents.”

“A primary responsibility of the Senate campaign committee is to support and see that incumbent Republicans are re-elected, and that’s true across the spectrum, and across the — the geography of our country,” Moran said then. “So, absolutely we’re 100 percent committed to Sen. McConnell’s re-election” and that of other incumbents, he said.