"I am officially seeking the Constitution Party nomination for governor of Colorado," Tancredo announced on Monday
If selected by his new party to be their nominee, he will run against the winner of the Republican primary, Democratic candidate John Hickenlooper, who is running unopposed, and against other third-party candidates in the November election.
Tancredo says he expects the race this fall to be "ugly."
The current Constitution Party gubernatorial candidate, Ben Goss, will need to leave his campaign in order for Tancredo to fill the vacancy.
If Goss does resign, Tancredo will have to register with the party, pay his annual dues and then be selected to fill the spot.
9NEWS spoke with Tancredo on Monday. He says he offered the ultimatum and decided to run because he feels Coloradans need another choice.
"What are my options? Sit back and watch us hit the iceberg? I do not have anything else I can do," he said. "The opportunity for me to do something for this state and affect the outcome in a positive way, from a conservative standpoint, was to do what I just did. There really were no other alternatives."
The announcement comes after Tancredo gave Republican Party candidates Scott McInnis and Dan Maes until noon on Monday to pledge to drop out of the race after the primary if the winner is trailing Hickenlooper in the polls.
Tancredo's demands came after McInnis became entangled in plagiarism charges and Maes was fined for campaign violations.
"This is the only option I have to give another, at least another choice, to the people of the state of Colorado," he said. "I have great love for this state. I do not want to see Hickenlooper as the governor. He's a very nice guy, but he's a very liberal Democrat. We've had enough of that. This whole place behind us here [the State Capitol] is run by them. Does anybody think it's better off today? 'Are you better off today?' That old saying. And the answer is: no."
Colorado GOP Chairman Dick Wadhams and Democratic Party Chair Pat Waak agree that Tancredo seems to be doing this for attention.
"I think it's motivated only by the need for personal attention from the national media and the Colorado media. I don't think it's grounded in any kind of reality," Wadhams said.
"I think it's all about Tom Tancredo and how much media he gets. That's my thought. He just wants everyone to pay attention to him," Waak said. "In the end, it's our responsibility to have the best candidate running for governor, and we think we do with John Hickenlooper. So, we're going to focus most of our attention on making sure that Hickenlooper's message gets out to voters, and that they vote for him in the fall"
Wadhams, who says he has known Tancredo for 40 years, considers their friendship to be strained due to this ordeal.
"I'm very frustrated with him. Never in my wildest dreams did I think he would be this selfish," Wadhams said. "Whether he is going to get into this governors race and talk about bombing Mecca, as he has in the past, impeaching President Obama, those are things that are distractions from the agenda to elect somebody other than John Hickenlooper. And the trouble with that is that it will take focus off the democrats and their failed policies."
In response to the ultimatum, McInnis issued a statement on Monday around the time of Tancredo's deadline:
"This election is about job creation, a stronger business climate, an end to unconstitutional tax increases and a commitment to reduce the size and scope of state government. We have elections to battle out competing visions for Colorado's future, and our fellow citizens are voting in the primary today as they have been for the past week.
"Those looking for a deadline should focus on the only real deadline: August 10 at 7 p.m. This is when the polls close, the people have voted and their votes are counted. That's the way the system works in a free society.
"Colorado Republicans will speak with their votes on that day, and I will abide by their decision."
Political analysts say the entry of Tancredo to the race will change everything.
"The impact on the governor's race here for Republicans will be devastating," 9NEWS political analyst, Floyd Ciruli said. "This will look a lot like 1992. You had George Bush Sr. and Ross Perot. They split the Republican vote."
Tancredo said in an interview on Saturday that the possibility of that happening is a concern.
"Sure I'm afraid of that. That's why I have to start now. I can't wait. I have to start a campaign as quickly as possible, raise as much money as possible and fight as hard as I can," he said.
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