Mihajlović ran for the Zemun municipal assembly in the 2000 Serbian local elections and was defeated.[4][5] This was this last local election cycle in Serbia in which members were elected for single-member constituencies; all subsequent cycles have taken place under a system of proportional representation.
The 2000 local elections took place concurrently with the 2000 Yugoslavian presidential election, in which longtime authoritarian leader Slobodan Milošević fell from power after being defeated by Vojislav Koštunica. The Serbian government also fell after Milošević's defeat and a new Serbian parliamentary election was called for December 2000. Mihajlovič received the 189th position on the Radical Party's electoral list; the list won twenty-three seats, and she was not chosen for a mandate.[6] (From 2000 to 2011, Serbian parliamentary mandates were awarded to sponsoring parties or coalitions rather than to individual candidates, and it was common practice for the mandates to be assigned out of numerical order. Mihajlović could have been included in her party's delegation despite her low position on the list, though ultimately she was not.)[7]
She later appeared in the twenty-fifth position on the Radical Party's list for the Belgrade city assembly in the 2004 Serbian local elections.[8] The list won twenty-seven seats, and on this occasion she was assigned a mandate.[9][10] The Democratic Party (DS) and its allies won the election, and Mihajlović served in opposition for the next four years.
She was given the twenty-eighth position on the Radical Party's list in the 2008 parliamentary election and the fifth position on its list for Belgrade in the concurrent 2008 local elections.[11][12] She did not receive a mandate to serve at either level.[13][14][15]
The Radical Party experienced a serious split later in 2008, with several prominent members joining the breakaway Serbian Progressive Party (SNS) under the leadership of Nikolić and Aleksandar Vučić. Mihajlović remained with the Radicals.
Serbia's electoral system was reformed in 2011, such that all parliamentary mandates were awarded to candidates on successful lists in numerical order.[16] Mihajlović received the ninth position on the Radical Party's list in the 2012 parliamentary election and was promoted to the third position in 2014.[17][18] The party did not cross the electoral threshold for assembly representation on either occasion.
She was again given the third position on the SRS list for the 2016 parliamentary election and was this time elected when the party won twenty-two seats.[19] The SNS and its allies won a majority victory, and the SRS served in opposition. During her parliamentary term, Mihajlović was a member of the committee on the Serbian diaspora and Serbs in the region, a deputy member of the committee on human and minority rights and gender equality, and a member of the parliamentary friendship groups with Armenia, Belarus, China, and Venezuela.[20]
She again appeared in the third position on the Radical Party's list in the 2020 parliamentary election and was promoted to the second position for the 2022 and 2023 elections.[21][22][23] On each occasion, the party failed to cross the electoral threshold.
In May 2022, Vojislav Šešelj received a summons to appear before the International Residual Mechanism for Criminal Tribunals (IRMCT; the successor body to the ICTY) to respond to charges concerning the publication of classified information and the names of protected witnesses. The summons also included the names of seven current and former Radical Party officials, including both Mihajlović and her husband.[24] The IRMCT ultimately filed an indictment against Šešelj, Ljiljana Mihajlović, Ognjen Mihajlović, and two other Radical Party officials on 11 August 2023. In late February 2024, the presiding justice transferred the case to Serbia for trial.[25] The matter is ongoing.