Macias ran for the state House in the March 2006 Republican primary. He garnered financial support of the Texas Republican Legislative Campaign Committee, a pac that San Antonio physician and conservative political activist James R. Leininger personally gave over a million dollars. While Leininger intended to avoid attention regarding his role in the campaign, he was only large contributor to the PAC and nearly the sole source of campaign funds to the virtual newcomer Macias. Texas Republican Legislative Campaign Committee was created shortly before the election although it appeared from campaign contracts that the Leininger shell was laying the ground work months earlier. Leininger is also the founder and principal contributor of the Texas Public Policy Foundation. By a margin of only forty-six votes, Macias unseated the two-term incumbent, Carter Casteel, a former Comal County county judge. He polled 10,183 votes to her 10,137 ballots. In the 2008 Republican primary, again where almost sole source came Leininger sources, Macias was defeated for a second term by Doug Miller, a former mayor of New Braunfels. Miller received 14,684 votes to Macias' 14,667, a margin of 17 votes.
Key legislative votes
In the 2007 legislative session, Representative Macias supported enhanced voter identification requirements; the new procedures finally took effect after many legal hurdles with the primary elections on March 4, 2014. He voted for the legislative ban on human papillomavirus vaccines though Governor Rick Perry had advocated compulsory immunizations of sixth-grade girls as a preventative against sexually-transmitted diseases. Macias voted against a pay increase for public school employees, but the measure passed, 90-56. He co-sponsored a bill to permit religious expression in Texas public school but did not vote on final passage, when the measure was approved by the House, 107-28. He voted against allowing casinogambling on Indianreservations; the measure deadlocked 66-66 ikn the House, with 18 members not voting.
Macias, who was voted by colleagues as "Freshman of the Year" in 2007, was a legislative ally of former Speaker Tom Craddick of Midland. As Macias left the House, the members voted to replace Craddick with the more moderate Representative Joe Straus of San Antonio. Macias issued a statement to constituents opposing the change in Speakers:
I have served with Joe Straus and have some true concerns. He is not conservative. Therefore, I don't think he will be the best representative of leadership for conservative Republicans or our great state.
Legislative ratings
As a legislator, Macias was rated 97 percent conservative in 2007 by Phyllis Schlafly's Eagle Forum, which is maintained in Texas by Cathie Adams, a former state chairman of the Texas Republican Party. Macias ranked 45 points higher than Carter Casteel's rating for her last term and 26 points higher than his successor Doug Miller in the 2013 session. The Young Conservatives of Texas ranked Macias 92 percent, compared to 53 percent for Casteel and 64 percent for Miller. He was rated 93 percent by Texans for Fiscal Responsibility, compared to 47 percent for Miller. The National Abortion Rights Action League ranked him 0 percent in 2007 but gave Casteel a 27 percent score. The Texas League of Conservation Voters rated him 38 percent.