ANKENY, Iowa -- Democratic presidential hopeful Bernie Sanders, who’s been put on the defensive by Hillary Clinton over his record on guns in recent days, sought to turn the tables on the party’s front-runner Sunday night.

At the outset of a rally here that drew about 800 people, the Vermont senator ticked off several issues on which he and Clinton are not completely in sync -- family leave, Social Security and a proposed crude oil pipeline in Iowa -- and challenged the former secretary of state to adopt his positions.

Clinton and Sanders’s attempts to more aggressively draw contrasts with one another come as polls show the race between the two leading Democrats tightening in Iowa and New Hampshire just weeks before voting begins in the first nominating contests.

It’s unclear how much traction Sanders might get on the issues he chose to highlight Sunday night, however, given the nuanced nature of some of the differences with Clinton.

Sanders, for example, supports legislation pending in Congress that would guarantee workers three months of paid family and medical leave. The benefit would be paid for by an increase in payroll taxes that Sanders says would cost the average worker $1.61 a month.

“I would hope Secretary Clinton joins us in fighting for that proposal,” Sanders told his audience, noting that the plan is popular among progressive lawmakers.

Clinton has voiced support for the same goal but balked at the idea of paying for it by raising taxes on lower-income workers, even modestly. She has promised not to raise taxes on those making less than $250,000 a year and argued that guaranteed family leave could be funded another way.

Sanders also talked up his desire to expand Social Security benefits for low-income seniors, a move that he would finance by raising taxes paid into the system by people with incomes more than $250,000 a year. Clinton has said she wants to expand benefits for some seniors but has not fully embraced the same proposal to pay for it.

Sanders also cited his opposition Sunday to a proposed crude oil pipeline that would run from Iowa’s northwest corner down to its southeast corner. Clinton has not voiced a firm position on the so-called Bakken pipeline but said her “heavy bias is in favor of moving away from fossil fuels, however they are delivered.”

In the Democratic contest, the past few days have been dominated by sparring over Sanders’s 2005 vote for legislation to grant gun manufacturers and dealers immunity from lawsuits when their products are used to commit a crime.

Clinton, who opposed the measure while a senator representing New York, has repeatedly said that the vote -- and gun control more broadly -- is a key difference with Sanders.

Sanders has indicated he is willing to revisit the immunity law provided protections are left in place for “mom-and-pop” gun stores.

On Sunday, Sanders accused the Clinton campaign of going after him on guns because it is “panicky” over tightening polls.