Secretary of State Mike Pompeo’s decision to rule out a run for the open Senate seat in Kansas gives a major boost to fellow Republican and former Kansas Secretary of State Kris Kobach -- a favorite among immigration hawks who is promising to bring a tough line on both legal and illegal immigration to Washington if elected.

“My approach to immigration is one that puts the American national interest first, both with respect to legal immigration and with respect to ending illegal immigration,” Kobach told Fox News in a phone interview.

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Pompeo had been urged to consider running to replace outgoing Sen. Pat Roberts, having represented Kansas in the House between 2011 and 2017 before becoming CIA director. But despite fueling speculation of a bid with numerous visits to Kansas, a source told Fox News this week that Pompeo told Senate Majority Leader Mitch McConnell, R-Ky., that he would not be running.

Kobach is seen as the favorite for the party’s primary, but Pompeo could have shifted him out of that spot if he had elected to run. With the latest development, Kobach is optimistic about his chances in the primary and subsequent election in November.

“It transformed what would have been a very long slog and a tough fight into a different type of race,” he said. “The current position I’m in now, if you believe the polls, is a good one.”

The boost for Kobach is also good news for immigration hawks in the party, some of whom have been frustrated at what they see as a failure by the Trump administration to be as forceful as they’d like both in cracking down on illegal immigration and in restricting some forms of legal immigration.

Kobach has long argued for more hawkish policies on immigration. He spearheaded voter I.D. laws as secretary of state and is on the board of “We Build the Wall” -- a private group building its own sections of wall along the southern border. When asked what he’d fight for if elected to the upper chamber, he rattled off policies including ending the diversity lottery visa -- which provides visas to countries with low rates of immigration to the U.S. -- and implementing mandatory E-Verify nationwide -- which would force employers to confirm the legal immigration status of their employees.

He’d also urge a tougher line on so-called sanctuary cities -- jurisdictions that refuse to comply with detainers from immigration enforcement authorities. He says that while there has been some efforts to go after sanctuary cities by the administration and some in Congress, it hasn’t been enough.

“There’s already a federal prohibition in federal statute against sanctuary cities but it doesn't have any teeth so I’d seek to put teeth in that and I have an idea of how that can be done through threat of civil lawsuits, through loss of federal funds and the like,” he said.

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Kobach also wants to re-examine the legal immigration system more broadly, re-orientating it to what he describes as an “America First” outlook. He’s a supporter of Sen. Tom Cotton’s, R-Ark., RAISE Act that would establish a skills-based points system and reduce extended forms of family-based immigration. Kobach also wants to focus on restricting companies who are using the legal immigration system to bring in cheap labor to replace American workers.

“You can also do a number of things to ensure certain industries aren't bringing in hundreds of thousands of foreign workers when American graduates in those exact same fields are unable to find jobs,” he said. “And in some parts of the tech sector you see that happening, and these are areas where the American national interest is not being served and you have to have a deep understanding of immigration policy and immigration law that so many don't have.”

Kobach, who cites his past experience teaching constitutional law and as a clerk on the 10th Circuit Court of Appeals, also wants to help the president in picking originalist judges to courts.

“President Trump has done a tremendous job transforming the courts to a more originalist outlook, but he does need help in the Senate to continue on that path,” he said.

“President [George W.] Bush nominated a number of judges who ended up being activists indistinguishable from [President Barack] Obama nominees, and usually it helps for presidents to have a backstop in the Senate -- several senators who perform very significant and deep vetting, so if someone in the White House Counsel's office slips up and nominates someone who is not a judicial originalist, hopefully a senator can catch that person,” he said.

The support from fellow hawks is rock solid. Conservative author Ann Coulter was reported to have lobbied Trump to pick Kobach as his running mate in 2016. In April she scolded Trump for not having appointed Kobach to the Department of Homeland Security.

“Trump's immigration agenda is a full-blown catastrophe because putting anyone other than Kris Kobach at DHS is like having the [American Civil Liberties Union] advise him on judges, instead of the Federalist Society,” she tweeted.

NumbersUSA, a group that seeks to reduce levels of immigration said in April that there was "no one more qualified" to head DHS than Kobach. RJ Hauman, head of government relations at the Federation for American Immigration Reform (FAIR), told Fox News that Kobach has "fought for years for American workers and secure borders."

Kobach, who backed Trump in 2016 and who served on his transition team, praises the administration's work on a number of immigration-related issues, including its successful fight for the travel ban for residents of certain countries deemed high-risk, as well as building what it has of the wall in the face of congressional hurdles. He also backs the implementation of the Migrant Protection Protocols (MPP) which sees migrants sent to Mexico to await their immigration hearings.

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But he argues that some officials in the executive branch over the last three years have “dragged their feet” on implementing policies he says he knows Trump favors -- including ending birthright citizenship. He also places a lot of blame on Congress for why some policies have not been implemented.

“There are many things President Trump wants to get done that requires congressional action and Congress has completely failed in those areas -- in things like changing priorities toward skill-based immigration, ending the diversity lottery visa, implementing E-Verify, stopping sanctuary cities,” he said. “There are a host of areas like that where he can't do it with the executive branch alone, he needs congressional help and that help has not been there.”

Kobach is a controversial figure among not only Democrats, but also with some Republicans both in Kansas and in Washington D.C. He faces a primary field that includes Rep. Roger Marshall, R-Kansas -- who, according to Roll Call, has racked up $250,000 for his campaign in the days since Pompeo said he wouldn’t run.

Kobach is likely to face significant opposition from GOP leaders in the capital, who fear that his hardline stances could make the seat vulnerable to be flipped by a Democrat. Kobach lost the Kansas governor’s race in 2018 to Democrat Laura Kelly after he beat sitting Gov. Jeff Colyer in a primary.

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"Just last year Kris Kobach ran and lost to a Democrat. Now, he wants to do the same and simultaneously put President Trump’s presidency and Senate Majority at risk," Joanna Rodriguez, press secretary for the National Republican Senatorial Committee, said in July. Bloomberg News reported that McConnell this week met with Marshall. Others are calling for other candidates to rally behind an anti-Kobach candidate.

“Everybody but Kobach probably should get together and say, ‘Now why are we doing this and what are we trying to gain?' And pick somebody and go head-to-head," Tim Shallenburger, a former Kansas Republican Party chairman and state treasurer, told The Associated Press.

But Kobach said there was a significant difference in that the gubernatorial race is often focused on issues such as education funding, and therefore the governor's seat regularly goes back-and-forth between parties. The Senate seat, meanwhile, has stayed firmly red for years.

"On federal issues Kansans lean more strongly to the right, so I think the outcome is likely to be different and our models indicate it is going to be different,” he said.

Fox News' Gregg Re, Rich Edson and The Associated Press contributed to this report.