GRAND RAPIDS, MI — It's been a relatively quiet spring from U.S. Rep. Justin Amash's campaign, though it's better not to expect the same ahead of the Aug. 5 primary.

The incumbent Republican said he'll soon be gearing up to defend his bid for reelection against challenger Brian Ellis, who has been running advertisements against the congressman on West Michigan television for months. As the summer heats up, expect the rhetoric among the camps to increase, too.

Toward the end of May, the Michigan Information and Research Service, or MIRS tracked Amash and Ellis at 42 percent over 23 percent, respectively.

Amash, R-Cascade Township, told MLive and The Grand Rapids Press late last week that his lead is sustainable while the Ellis campaign has tried to paint the lead as one that is shrinking with each new poll.

Both agree MIRS' survey parallels internal numbers measured by each of the campaigns.

"I feel very confident going into election day," Amash said. "If I were Ellis, I wouldn't be bragging about being down 19 points."

The race is marked by the candidates' widely different ideologies, and it already has been highlighted by national media outlets as mirroring the national rift between tea party and "establishment" Republicans.

The more libertarian Amash is well-known to break from his party, sometimes putting he and a few like-minded colleagues in Congress in the slimmest of minorities. Ellis has pounced on several Amash votes that he claims neither align with voters in the Third Congressional District nor the Republican Party.

And even in his heavily Republican congressional district, Amash is forced to defend his sometimes controversial positions despite widespread popularity among more conservative constituents.

Take, for example, the issue of abortion. Amash voted "no" on the 2012 Prenatal Nondiscrimination Act, arguing it would not have outlawed a single abortion. Ellis said the vote showed he didn't support "the life agenda."

A recent Ellis TV ad criticized Amash for voting against a balanced budget amendment, a piece of legislation Amash argued wasn't conservative enough and had to be written "the right way."

Amash hasn't been without ads supporting his cause, as conservative interest group Club for Growth stood by his side in January with one calling Ellis a "corporate-loving politician." The group spent more than $100,000 for the spot.

"I'm not sure there's any Republican in the country running on the issues he's running on — he might be the only one — and they are not popular positions with Republicans," Amash said.

In response, Ellis campaign spokeswoman Megan Wells said this goes to show how Amash is out of touch with the district's voters.

"Justin Amash is so out of touch that he criticizes Brian Ellis for supporting a Balanced Budget Amendment, keeping terrorists locked up in Guantanamo Bay, and being endorsed by Right to Life," she said in an email.

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Andrew Krietz covers breaking, politics and transportation news for MLive | The Grand Rapids Press. Email him at akrietz@mlive.com or follow him on Twitter.