DENVER — When lawmakers are back at work in 2019, there will be three new Senators that were not voted on from an election ballot.

Three Senators have recently submitted their resignations - Sen. Matt Jones, D-Louisville, Sen. John Kefalas, D-Ft. Collins, and Sen. Daniel Kagan, D-Cherry Hills Village.

All three still have two years left on their four-year term.

Jones ran for Boulder County Commissioner in November and won, just as Kefalas did in Larimer County. Kagan is simply resigning.

"I was beginning to feel in need of a little relaxation of the work pressure, a relaxation of the schedule," said Kagan. "If you're not able or willing to give absolutely 100 percent, you should let someone else have a go."

Kagan is the lawmaker who was accused of using a women's restroom in the Capitol in 2017. An investigation found that he likely used the bathroom three times, though he said he accidentally used it once when it was unmarked.

So, is this why Kagan is calling it quits?

"Not at all. That was a little tempest in a teapot that was blown up into a big thing about an incident a couple of years ago. No, that had no bearing on it. It's a much more important decision than whether or not one has a little bit of a brouhaha over a triviality," Kagan told 9NEWS. "I'm comfortable with this decision, but it has nothing to do with the 'toiletgate' brouhaha."

Sen. Beth Martinez-Humenik, R-Thornton, is the lawmaker who filed the complaint against Kagan.

"I can't say for sure whether it had anything to do with it," Martinez-Humenik said about his resignation. "I never asked for a resignation or to be taken off committees or anything else. All that was asked was a public apology to all female staffers that were involved. He has not apologized to us. That's all that was asked for. How hard is it to say, 'I'm sorry, I'll never do it again?'"

When Kagan's replacement takes office, they may be the recipient of a term-limit-free two years. Colorado law states that if someone is appointed to fill a vacant state seat, the time in that position ​​​​​​does not count toward term limits if they serve less than half of that person's term.

State senators are allowed two four-year terms.

Kagan's resignation is effective Jan. 11, one week after the legislative session begins. He said he wants to stay to provide key votes to officially appoint the Senate President and Majority Leader.

Leaving after the session begins also opens the possibility that his replacement could serve the remainder of this term through 2020, and possibly be elected to serve two more terms through 2028.

"I certainly want my successor to go into the 2020 election with a record," said Kagan. "I don't know who's going to take my place, but if because of the date of my resignation, they have an opportunity to serve for longer than they would otherwise have, I certainly wouldn't regret that."

Jones made his resignation effective Jan. 1, and Kefalas made his on Jan. 2.

Jones told 9NEWS by phone, and Kefalas said in his resignation letter, that they hope their replacement is picked and sworn in on the first day of the session on Jan. 4.

To determine how much half of a term equals, you need to know the first day of the session in 2017 and the first day of the new session in 2021. Colorado law only states that the legislature must convene by the second Wednesday, so the first day in 2021 could be between Jan. 1 and Jan. 13.

If it was Jan. 13, anyone appointed after Jan. 14, 2019 would be serving less than half of the term.

If it was Jan. 1, anyone appointed after Jan. 2, 2019 would be serving less than half of the term.