The senator and 2016 GOP presidential candidate from Florida touted the plan as a novel approach to an issue on which Congress has not taken significant action, despite high-profile involvement by Ivanka Trump.
"This is important legislation. It is also unique," Rubio said at a news conference at the Capitol. "This is a dramatic readjustment of the way we deal with economic insecurity in the modern era."
Rubio's bill would allow parents of newborns to receive a Social Security benefit paying a portion of their wages for at least two months. Later in life, they would delay the date at which they begin receiving Social Security retirement benefits to make up for the amount withdrawn during their leave.
Ivanka Trump on Thursday welcomed Rubio's bill, though she played down expectations for action during this midterm election year.
"This was not exactly part of the Republican lexicon when we arrived in D.C. in January 2017," Trump said at an event hosted by Axios.
"Really at this point we're curating ideas with the hope of being able to build consensus, but it will take time," she added. "I'm cautiously optimistic that it can happen next year."
Rubio's proposal was immediately criticized by Democrats and some family-leave advocacy groups. Critics said the benefit was skimpy and condemned the idea of limiting beneficiaries' future retirement payments. They also noted that a majority of people who utilize the federal Family and Medical Leave Act (FMLA) do so to care for sick family members or when they themselves are seriously ill - not because of childbirth or adoption, which are the conditions covered by Rubio's bill.
"This proposal forces workers into an impossible position: If they need to cover a medical emergency today, then their Social Security benefits get cut when it's time to retire," Sen. Kirsten Gillibrand, D-N.Y., said in a statement about Rubio's bill. "If they need to take care of a sick or dying parent, as three out of four people who need paid leave would use it, they get nothing."
The FMLA guarantees 12 weeks of unpaid leave for anyone who works for the government or for a company with 50 or more employees. The United States remains unique in the developed world in not guaranteeing some form of paid medical or parental leave to workers, although a few states have passed paid-leave laws.
Gillibrand and other Democrats are supporting a competing proposal called the Family Act that would create a national paid-leave program with a small payroll tax. That legislation has failed to advance.
Rubio and Rep. Ann Wagner, R-Mo., who is introducing a companion bill in the House, described their legislation as a conservative approach that avoids new taxes or mandates on businesses that Republicans would oppose. However, after failing to reach agreement with some fellow GOP senators, Rubio introduced his bill Thursday without co-sponsors.
"I got impatient," Rubio said.
Family leave has become Ivanka Trump's signature issue in her father's administration. She has pushed him to talk about it in his State of the Union address and include it in his budget proposals. It has been taken up by a handful of Republicans, including Rubio and Sens. Mike Lee, R-Utah, Joni Ernst, R-Iowa, and Deb Fischer, R-Neb.
Progress thus far has been incremental. Fischer included a two-year pilot program in the GOP tax law that allows employers to claim a credit of as much as 25 percent of the wages they pay to employees who take time off under the FMLA; it applies to workers making under $72,000 annually.