Don’t mess with Texas, or so says the state’s famous phrase, but Democrats don’t seem to have gotten the word. They are committed to messing with Republicans in the GOP’s Lone Star State stronghold. Reliably red Texas has one of the most interesting Senate races this season and even party stalwarts are predicting a tight finish.

Republican Incumbent Ted Cruz is fighting off a strong challenge from Rep. Beto O’Rourke -- a rising star in Democratic ranks. Scar tissue from the 2016 campaign, combined with what one Republican described as a “stellar candidate” for Democrats, have made this race one to watch, even if flipping it will be tough.

A new NBC News/Marist poll shows that O’Rourke is within striking distance of Cruz among registered voters, trailing by just four percentage points. Both candidates are about even with independent voters, but O’Rourke does 10 points better with women and 11 points better with Latinos. He also has a whopping 35-point advantage among those who describe themselves as moderate. Cruz’s numbers are considerably behind those of Republican Gov. Greg Abbott, who leads his challenger, Lupe Valdez, by 19 points. Nonetheless, Cruz still leads in RealClearPolitics’ average of polls by 6.2 points.

Republicans say Cruz has a major branding problem and has not recovered from the nasty 2016 presidential primary season. One GOP strategist in the state said Cruz lacks support from Republican business leaders who have long seen him as “gumming up the works in D.C.” Meanwhile, many Donald Trump voters still don’t trust him after he declined to endorse the nominee during the Republican National Convention. Cruz finally endorsed Trump in a Facebook post a few months later.

“He had a lot of credibility and clout, especially among Republican voters. When he ran for president he did very well,” said the strategist. “But I think the Trump moment — when he didn't back Trump at the convention — was a turning moment for him.”

Cruz certainly had ample cause to resent Trump, reasons that went above and beyond losing the nomination to him. During the primaries, Trump dubbed Cruz “Lying Ted,” while questioning the sincerity of his religious faith. Trump issued a snarky tweet about the physical appearance of Heidi Cruz, while threatening to “spill the beans on your wife,” whatever that meant. Most bizarrely, Trump linked Cruz’s father with John F. Kennedy assassin Lee Harvey Oswald.

By way of response, Cruz called Trump “utterly amoral” and a “bully” who was “proud of being a serial philanderer.”

"This man is a pathological liar,” Cruz added. “He doesn't know the difference between truth and lies. In a pattern that is straight out of a psychology text book, he accuses everyone of lying."

The decision to finally back Trump, and to work with him as president, was seen as a political necessity, but some Republicans say it added to Cruz’s authenticity problem. A second Republican strategist in the state said authenticity remains Cruz’s biggest negative and is a reason why his numbers have taken a dip. “After the presidential race he’s a complete known entity -- and people, by and large, have made a judgment about him,” said the strategist, adding that a second-place finish in the GOP presidential race did the senator “zero favors.”

Cruz’s former political director, Jon McClellan, disagreed. “I think right after the presidential race there was a much-needed cooling down period for everyone,” he said. McClellan said Cruz did the right thing to try and unite the party and has helped the president accomplish major policy achievements, such as tax reform and advancing conservative Supreme Court nominees, which matter greatly to Texas voters. When asked about the closeness of the race with O’Rourke, McClellan said Cruz tends to underperform in polls ahead of Election Day, but wins in the end.

Most strategists agree, however, that this is a real race with a real opponent and that the senator will need to campaign effectively to win. They disagreed, however, about how Trump will play in this race. Some said a presidential campaign trip would galvanize Republican base voters. Others, pointing to the president’s legal troubles, aren’t so sure. “With an endless stream of bad headlines surrounding Trump's legal woes on the horizon, Cruz and other Republicans have to bet that voters will pay attention to the strong job numbers and economy, as much as the soap opera happening in Washington,” one strategist said.

The official party line is that Cruz’s history of working with the White House will be an asset. “The success President Trump, and the Republican-led Congress, has brought to the economy is incredible,” said Sam Pohl, communications director for the Texas Republican Party. “There are more jobs and higher confidence in the economy.” He also noted that Cruz has said he’d welcome the president to the state for a campaign visit.

For their part, Democrats are buoyed by the support they are getting from undecided voters, and say the O’Rourke-Cruz race is the matchup they’ve been waiting for. “It’s the entire Republican brand that’s the problem, including Ted Cruz,” said Manny Garcia, deputy executive director for the Texas Democratic Party. He added that the party has been working on building up its influence in the state for the past few election cycles and that officials believe O’Rourke is the candidate that can take them over the hump.

Garcia also pointed out that Texas became a single-digit state for Republicans in 2016 when Trump won there by only nine points. When asked if a visit from the president to buck up the GOP base would simultaneously mobilize Democratic voters, Garcia replied, “I’ll roll out the blue carpet for him if he wants.”