Markets in Japan have been thrown into a new period of volatility after the surprise election of Sanae Takaichi, a pro-stimulus conservative hard-liner, in the contest to lead Japan’s long-governing Liberal Democratic Party.

Ms. Takaichi, who is on track to become prime minister later this month after her Saturday victory, distinguished herself from her campaign rivals with a distinct policy vision for Japan’s economy, the world’s fourth-largest.

Though she softened her messaging significantly in recent days, Ms. Takaichi, an acolyte of former Prime Minister Shinzo Abe, has long embraced the view that Japan should return to so-called Abenomics, which promoted more government stimulus and easy-money policies.

Speculation that she would implement a form of “neo-Abenomics,” including low interest rates, led the yen to weaken sharply against the dollar on Monday morning in Asia.

Years of ultralow interest rates have meant that many investments in Japan have offered smaller returns than other countries, like the United States. That, in turn, has caused investors to sell yen to buy higher-paying foreign assets, flooding the market with yen and driving its price down.

Also on Monday, Japan’s benchmark Nikkei 225 stock index rose around 4 percent in early trading. Investors bet that a weak yen, which boosts the competitiveness of Japanese products overseas, would be a boon for domestic exporters. Government spending and various tax-cut plans promoted by Ms. Takaichi are also expected to bolster the economy in the short term.

Analysts said markets on Monday were also factoring in Ms. Takaichi’s defeat of Japan’s agriculture minister, Shinjiro Koizumi, who was considered a bigger proponent of curtailing government spending.

In her first bid to become leader of the Liberal Democratic Party, Ms. Takaichi promoted economic policies that diverged significantly from those of other party members. At one point last year, she said that the Bank of Japan’s rate hikes were “stupid.”

Her comments clashed with recent messaging from the central bank. Its governor, Kazuo Ueda, has said that it would continue to gradually raise interest rates. Japan’s policy rate remains at just 0.5 percent, despite inflation that has exceeded the bank’s 2 percent target for well over three years and dragged on private spending.

There had been growing speculation that the Bank of Japan might raise interest rates at its next policy meeting, set for the end of this month. With Ms. Takaichi’s election, market participants now see that as less likely.

The central bank will probably “wait and see” how Ms. Takaichi’s policymaking develops, said Takahide Kiuchi, the executive economist at Nomura Research Institute. “At this point, it is highly likely that the Bank of Japan will raise interest rates in December,” he said.

During her campaign for the party leadership, Ms. Takaichi softened her tone on interest rates, acknowledging that the central bank was responsible for monetary policy. At the same time, she said on Saturday after her win, the government and the Bank of Japan should move in “lock step.”

Ms. Takaichi also said on Saturday that she would not try to renegotiate the trade deal that the current administration reached with President Trump, despite having said during the campaign that she was interested in potentially doing so.